My old One Plus One suddenly refuses to boot without any changes from my side. OS is CyanogenMod 11. The device is rooted and there is TWRP 2.8.0.1 installed on it and debugging is active. The symptoms are as follows:

Once turned on the 1+ logo is briefly displayed as usual

Then the CM logo which looks like a turning bolt is shown indefinitely

I can boot to TWRP recovery mode. However, before attempting a factory reset I would like to do a backup with TWRP. This goes well for /system but fails for the /data partition. There are error messages Unable to stat 3 files. /data/data/com.android.providers.settings,
/data/data/com.android.settings/databases/google_analytics_v2.db-journal
and /data/data/com.android.settings/files.

When I try to make a backup with adb, I get stuck at the stage where I am supposed to confirm the backup on the phone itself.

Is there any possibility to enforce the adb backup and skip the confirmation? Any other means of making a backup od App date prior to attempting factory reset? Are there any other forms of backup which I could use?

I am also thinking about pulling the entire /data/data directory to my computer via adb. Would this be a viable option for restoring data later?

The CyanogenMod 11 may not even touch DATA/ however that is obviously what is causing the issue... corruption. Try flashing the stock Cyanogen Zip you used to update... and then Do Not Wipe Data... Just Dalvik Cache & Cache ... Try the system repair first... Then see if it is actually DATA or SYSTEM causing problems....
– Gadget GuruMar 22 at 20:23